a) Field of the Invention:
The present invention relates to a light phase difference measuring method using an interferometer.
b) Description of the Prior Art:
Available as the conventional phase difference measuring methods using interferometers are the fringe scanning method, heterodyne method, Fourier transform method, etc. (Optics 13 (1984) 55) which are used for measuring surface roughness, aspherical surfaces, refractive index distributions in unhomogenous media and so on. For measurements with higher accuracy, these conventional measuring methods require measurements of intermediate intensities between locally maximum lightness and locally minimum lightness in intensity distributions on produced interference fringes. When light receiving elements used for measurement have insufficient linearities, when interference fringes are affected by noise or when contrast is low on interference fringes in measurements of the intermediate intensities, however, the conventional methods do not permit accurate measurement of intensity distributions and may provide inaccurate values of phases.